KR102614222B1 - Apparatus and method for indirect surface cleaning - Google Patents

Abstract

A photomask includes one or more features placed on it. One or more features have an associated design position, and the distance between the position of the one or more features and the associated design position defines the position error of the one or more features. A method of improving the performance characteristics of a photomask includes directing electromagnetic radiation toward the photomask, the electromagnetic radiation having a wavelength that substantially matches the high absorption coefficient of the photomask; generating an increase in thermal energy in the photomask through incidence of the electromagnetic radiation; and reducing the position error as a result of increased thermal energy in the photomask.

Description

Indirect surface cleaning device and method {Apparatus and method for indirect surface cleaning}

Cross-reference to related applications

This patent application is a continuation-in-part of U.S. Application No. 14/294,728, filed June 3, 2014; US Application No. 14/077,028, filed November 11, 2013, now a continuation of US Patent No. 8,741,067; U.S. Application No. 13/657,847, filed October 22, 2012, now a continuation of U.S. Patent No. 8,613,803; U.S. Application No. 12/277,106, filed November 24, 2008, now a continuation of U.S. Patent No. 8,293,019; U.S. Application No. 12/055,178, filed March 25, 2008, now a continuation of U.S. Patent No. 7,993,464; Priority is claimed on U.S. Provisional Application No. 60/954,989, filed August 9, 2007, the entire disclosure of which is incorporated herein by reference.

This patent disclosure broadly relates to a surface cleaning apparatus and method, and more specifically to an apparatus and method for cleaning the surfaces of components used in the semiconductor industry, optical systems, etc. The devices and methods disclosed herein can be applied to extend the useful life of a photomask reticle, improve the performance of a photomask reticle, or a combination thereof.

Photolithographic production of semiconductors uses a series of photomasks to create features on a semiconductor wafer. At each photolithography step, a photomask is imaged onto the fabricated semiconductor wafer. Once the photomask is imprinted on the wafer, additional processing can be used to modify the semiconductor wafer material into the pattern of the photomask. In subsequent steps, additional photomasks may be imaged on the wafer. The quality of structures fabricated on a semiconductor wafer is improved due to the high-precision alignment of subsequent photomasks compared to features created using previous photomasks. Metrics that evaluate the quality of structures fabricated on a semiconductor wafer may include dimensional accuracy of a single feature, dimensional accuracy of the position of one feature relative to other features, or a combination thereof. Some dimensions of features on the photomask may be referred to as critical dimensions (CD), and the placement of features on the photomask relative to other features may be referred to as overlays. For the most critical photomasks, overlay requirements can be a few nanometers or less over the entire length of the mask.

Photomask properties, such as dimensional properties and material properties, may vary within ranges resulting from, for example, tolerances imposed during the manufacturing process. For example, the optical performance characteristics of a partially absorbing film may vary depending on the material composition of the film and the thickness of the film. Additionally, the CD and overlay of the mask may vary depending on the precision of the write tool, the number and type of etching process, cleaning process, and the temperature and stress applied to the photomask during manufacturing. Variability in the properties of the untreated photomask (such as composition and stress differences in the film) can contribute to the final variation of the CD and overlay by changing the photomask's response to the manufacturing process.

Mask-to-mask differences ultimately lead to changes in products created using photomasks. For this reason, limits or ranges of performance criteria are applied to distinguish between photomasks that are acceptable for production use and those that are defective. If the photomask's performance falls outside acceptable limits, the photomask is rejected and another mask is manufactured.

In addition to manufacturing variations, the performance characteristics of a photomask may change due to use in production. During use in production, photomasks may be exposed to intense radiation, including ultraviolet (UV) radiation, deep ultraviolet (DUV) radiation, or extreme ultraviolet (EUV) radiation. Such radiation can cause light degradation, especially of thin film photomasks. Additionally, photomasks may require cleaning after being used in production for a period of time. These cleaning processes can change the properties of the photomask and may limit the number of times the mask can be recleaned and still meet specifications.

Processes that reduce mask-to-mask variability for one or more critical process characteristics of a photomask can potentially improve the overall production yield of a semiconductor manufacturing process using a photomask. First, fixing out-of-spec masks and making them viable for production use can help avoid production delays and costs associated with manufacturing new photomasks to replace out-of-spec photomasks. Second, reducing the variation in one or more performance characteristics can provide a margin of tolerance that can be used to extend the acceptable range of other characteristics. Therefore, reducing the variability of certain important photomask properties can provide the advantage of reducing the variability of printed features on the product wafer, which improves device yield and performance.

As an example, it may be advantageous to improve the overlay of the photomask to improve the precision of feature placement on the wafer, which can be used to correct out-of-spec masks, thus improving the yield of the mask. Additionally, it may be advantageous to reduce mask-to-mask variation in the overlay for a set of masks printed on the same wafer. By improving the arrangement of features on the wafer from multiple masks, it becomes possible to accommodate other imperfect increases in the variability of other important parameters.

As the photomask industry moves toward multiple patterning, requirements for overlay precision between critical mask layers are increasing. In multiple patterning, two or more masks are used in combination to create reduced feature sizes on the printed wafer. Due to the reduced feature size, reduced errors in individual masks and reduced overlay errors between mask sets may be required. Therefore, it is particularly advantageous to develop processes to improve overlays on photomasks used for multiple patterning.

It will be understood that this background information has been prepared by the inventor to aid the reader's understanding, and should not be taken to indicate that any of the foregoing problems per se are known in the prior art.

Considering at least the above discussion, it would be advantageous to develop a process that can improve the overlay of a photomask by treating it before, during, or after the manufacturing process of the photomask.

Additionally, it would be advantageous to develop processes that can improve the overlay of photomasks to recover the changes created by their use in production.

Additionally, it would be advantageous to develop new methods and/or devices for modifying the overlay of photomasks to improve usability, performance, lifetime, or other aspects of use.

Additionally, it would be advantageous to develop new laser-based methods and/or devices for modifying the overlay of photomasks to improve usability, performance, lifetime, or other aspects of use with reduced potential for surface damage.

Additionally, it is advantageous to incorporate a method and/or device for modifying the overlay of a photomask in the photomask fabrication, wafer fabrication, and/or repair processes.

Additionally, it would be advantageous to develop a method and/or device to improve the overlay of a photomask by local or global thermal deformation of a partially absorbed film on the photomask surface.

Additionally, new laser-based methods for thermal modification of photomasks that improve overlays that also produce heat-based removal of surface contamination, improve usability, performance, lifetime, or other aspects of use with reduced potential for surface damage; and /Or it is advantageous to develop a device.

The foregoing needs are largely met by specific embodiments of the present invention. According to one embodiment of the present invention, a method is provided for modifying one or more properties of a material to affect its optical properties and/or affect the performance or lifetime of a device using the target material. In particular, a method for modifying the overlay of a photomask is provided. The method may include irradiating the substrate surface to generate thermal energy or heat accumulation in the substrate and/or thin film(s). The temperature increase resulting from the partial absorption film may include, but is not limited to, compositional changes (e.g., dehydration, oxidation), surface changes (e.g., morphology, roughness), or material property changes (e.g., annealing, densification). Creates heat-based material changes.

This method may include the use of electromagnetic radiation, and especially the use of laser radiation. The method of the present invention may include reducing the risk of thin film damage by using relatively long pulse widths or by heating the substrate and the thin film to similar temperatures by irradiation. This method provides improved photomask performance by local modification and/or uniform or non-uniform global modification of the photomask overlay.

This method may be advantageous for applications where the environment above the substrate is almost or completely enclosed. In such cases, the method may include directing a source of electromagnetic energy through a material disposed against a surface that is part of the substrate environmental enclosure. For example, the method of the present invention can be used to modify the overlay of a pellicalized photomask.

According to another embodiment of the present invention, an apparatus for modifying laser material using the method described above is provided. The device may include metrology for inspection of the photomask overlay. It may be advantageous to perform these measurements before, during, or after process application and can be used for closed-loop control of the process during use.

Additionally, the above-described devices may include means for monitoring and controlling the temperature of the substrate and/or adjacent materials. The means may include local temperature control or temperature control across the entire substrate.

According to another embodiment of the present invention, a photomask manufacturing process is provided using the methods and/or devices disclosed herein to modify the overlay of a photomask.

Certain embodiments of the present invention provide the ability to modify materials without surface preparation or environmental control over the substrate surface. Certain embodiments provide material modifications that reduce the risk of substrate damage. Additionally, certain embodiments of the present invention provide for extended life of photomasks used in wafer printing. Certain embodiments of the invention also provide increased precision in the manufacture of photomasks used in wafer printing. Additionally, certain embodiments of the present invention provide reduced wafer manufacturing costs while providing performance that results in improved photomask yield and improved device yield.

Accordingly, certain embodiments of the invention have been outlined rather broadly so that the detailed description herein may be better understood and its current contribution to the art may be better understood. Of course, there are additional embodiments of the invention which form the subject matter of the claims described below and appended hereto.

In this regard, before describing one or more embodiments of the invention in detail, it should be understood that the invention is not limited in its application to the arrangement of components mentioned in the following description or shown in the drawings. The present invention can be implemented and performed in various ways other than the described embodiments. Additionally, it is to be understood that the phraseology and terminology employed herein, as well as in the Abstract, is for the purpose of description and should not be regarded as limiting.

As such, those skilled in the art will understand that the concepts underlying the present disclosure can be easily used as a basis for designing other structures, methods, and systems for carrying out the various purposes of the present invention. Therefore, it is important that the claims be considered to include equivalent elements, provided they do not depart from the spirit and scope of the invention.

1A is a schematic diagram showing externally-generated thermal excitation of a partial absorber.
Figure 1b is a side view showing the absorbent thin film on the top of the substrate.
Figure 2 is a graph showing the MoSi absorption spectrum from the deep ultraviolet region to the far infrared region of the electromagnetic spectrum.
Figure 3 is a graph showing the absorption spectrum of quartz from the deep ultraviolet region to the far infrared region of the electromagnetic spectrum.
Figure 4 is a diagram showing a photomask surface with a partially absorbing thin film including a pellicle attached thereto.
Figure 5A is a schematic diagram showing a photomask with a pellicle showing a laser beam focused through the pellicle and onto the surface.
Figure 5b is a schematic diagram showing the beam spot size on the pellicle versus mask created by focusing.
Figure 5C is a schematic diagram showing a photomask with a pellicle showing a laser beam focused through the pellicle and on a surface, with the beam spot on the pellicle shown in side view.
Figure 6a is a cross-sectional view showing the Gaussian beam energy distribution and the corresponding temperature profile generated.
Figure 6b is a cross-sectional view showing the top-hat beam energy distribution and the corresponding temperature profile generated.
Figure 7 is a diagram showing a photomask with a cooling plate in contact with the bottom of the mask.
Figure 8 is a diagram showing forced convection cooling of a region on a photomask.
Figure 9a is a schematic diagram showing a single pass of a laser beam across a surface to minimize local thermal energy or heat accumulation. A single row or column is shown with large lateral spacing between the spots.
Figure 9b is a schematic diagram showing two passes of the laser beam across the surface to minimize localized thermal energy or heat accumulation. A single row with two sets of beam spots is shown overlapping with large spacing between pulse sets.
Figure 9C is a schematic diagram showing multiple laser passes over an area of a substrate to achieve material modification processing of a cross-section of the substrate.
Figure 9d is a schematic diagram showing the second dimension of material modification processing.
Figure 9E is a schematic diagram showing the use of discontinuous pulses on a surface.
Figure 10 is a schematic diagram showing a partial absorber on a substrate along with a thermocouple or infrared temperature monitoring device.
Figure 11 is a schematic diagram showing a partial absorber on a substrate along with an imaging, microscopy, spectroscopy or combination system for material characterization.
Figure 12 is a schematic diagram showing a partial absorber on a substrate with the measurement system in which the measurement system and laser beam delivery share a common path.
13 is a diagram showing a system for loading a substrate and moving the X/Y/Z stage to a laser beam.
Figure 14 is a plan view showing a photomask assembly according to one aspect of the present disclosure.
Figure 15 is a plan view showing a photomask assembly according to one aspect of the present disclosure.
Figure 16 is a plan view showing a photomask assembly according to one aspect of the present disclosure.
Figure 17 is a plan view showing a photomask assembly according to one aspect of the present disclosure.
Figure 18 is a plan view showing a photomask assembly according to one aspect of the present disclosure.
19 is a plan view showing a photomask assembly according to one aspect of the present disclosure.
Figure 20 is a plan view showing a photomask assembly according to one aspect of the present disclosure.
Figure 21 is a plan view showing a photomask assembly according to one aspect of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS Aspects of the present disclosure are now described in detail with reference to the drawings, in which like reference numerals refer to like elements throughout, unless otherwise specified.

Aspects of the present disclosure provide an apparatus and method for modifying the position of a feature on a photomask. 1A is a schematic diagram showing externally generated thermal excitation of a partial absorber. As shown in Figure 1A, the excitation device 100 includes an external energy source configured and arranged to direct an energy beam 2 onto an absorbing thin film 3 disposed on the surface of a partially or fully transmissive substrate 4. Includes (1). According to one aspect of the present disclosure, the excitation method may include direct excitation of the absorbing thin film (3) on the substrate (4) by an energy beam (2) generated by an external energy source (1). Substrate 4 may be a photomask or may constitute at least a portion of a photomask assembly, and unless otherwise specified, “substrate” and “photomask” are used interchangeably throughout this disclosure.

As described herein and unless otherwise specified, the partial absorber film is specially formulated to allow at least a portion of the lithographic light wavelengths to pass through the film to enhance the printing effect on the wafer. Accordingly, the partial absorption film may not include an opaque film.

According to one aspect of the present disclosure, the external energy source 1 is an electromagnetic energy source and the energy beam 2 is an electromagnetic beam. According to another aspect of the present disclosure, the external energy source 1 is a light source and the energy beam 2 is a light ray. According to another aspect of the present disclosure, the external energy source 1 is a laser light source, and the energy beam 2 is a laser beam. However, the external energy source 1 may use other forms of energy, including but not limited to electron beams, microwave beams, X-ray beams, acoustic waves, combinations thereof, or any other energy beam known in the art. It will be understood that it is possible to generate an energy beam 2 that implements.

Interaction between the energy beam 2 and the absorbing film 3 or the substrate 4 may cause thermal excitation of the absorbing film 3, the substrate 4 or a combination thereof. According to one aspect of the present disclosure, the interaction between the energy beam 2 and the absorbing thin film 3 results in an increase in the thermal energy of the absorbing thin film 3 material, which may cause an increase in the temperature of the absorbing thin film 3 material. there is. Alternatively or additionally, the interaction between the energy beam 2 and the substrate 4 results in an increase in the thermal energy of the substrate 4 material, which may cause an increase in the temperature of the substrate 4 material. In turn, when the temperature of the substrate 4 is greater than the temperature of the absorbing thin film 3, heat can be transferred from the substrate 4 to the absorbing thin film 3 by conduction, convection, radiation, or a combination thereof, thereby allowing absorption. The thermal energy or temperature of the thin film 3 is further increased.

As described herein, it will be understood that increasing thermal energy in a material may refer to an increase in enthalpy (h), an increase in internal energy (u), an increase in temperature, or a combination thereof.

FIG. 1B is a side view showing the absorbent thin film 3 on the substrate 4. In Figure 1b, the absorber film 3 is patterned so that a part of the substrate 4 is in communication with the external energy source 1 through the absorber film 3 disposed thereon, while other parts of the substrate are exposed to the absorber film 3. It communicates directly with the external energy source (1), without prior transmission of the energy beam (2) through (3). Accordingly, it will be appreciated that heat generated in a portion of the substrate 4 may be conducted through the substrate 4 before being transferred to the absorbing film 3 via conduction, convection, radiation or a combination thereof.

According to one aspect of the present disclosure, a method is provided for modifying one or more properties of a material to affect the material properties and/or affect the performance or lifetime of a device using the target material. In a non-limiting example, a method for modifying the location of a feature on a substrate is provided. In the case of the absorbent thin film 3 on the photomask 4, this method involves the absorption thin film 3 shifted by use in production, a cleaning process, or an external force applied to the photomask (e.g., attaching a pellicle to the photomask 4). ), the usable life of the photomask 4 can be increased. The method may include exciting the substrate surface to create a uniform increase in energy or temperature rise in the substrate 4 and absorber film 3. The resulting temperature increase in the substrate 4 and/or the thin film 3 may include, but is not limited to, changes in composition (e.g. dehydration, oxidation), surface changes (e.g. morphology, roughness) or changes in material properties (e.g. heat-based material changes that may include annealing and densification). Alternatively or additionally, changes in heat-based materials may result in changes to the optical performance characteristics of the photomask.

In addition to the laser, an external energy source (1) can be used. For example, the external energy source 1 may be any part of the electromagnetic spectrum, including microwaves, infrared radiation, near-ultraviolet radiation, deep ultraviolet radiation, extreme ultraviolet radiation, electron beam generators, X-ray generators, or combinations thereof. Depending on the device, it may include a lamp or other device capable of radiating energy.

The absorbent film 3 and substrate 4 may be made of or include many different materials. According to one aspect of the present disclosure, the substrate 4 can have absorbent film properties and can be targeted for material modification without the absorber film 3 disposed thereon. An increase in the temperature of the absorbent film 3 may result in a heat-based change in the material of the absorber film 3 and/or the properties of the absorber film 3, including, but not limited to, dehydration, oxidation, surface roughness, annealing, or combinations thereof. can be created.

According to aspects of the present disclosure, the critical temperature for modifying the absorber film 3 is below the temperature that would cause damage to the material of the substrate 4, thereby mitigating the risk of heat-based damage to the substrate 4. I order it. In some cases, aspects of the present disclosure reduce the risk of damage to the substrate 4 compared to other substrate or film modification techniques because relatively long pulse widths can be utilized which can reduce the potential for multi-photon absorption processes. You can also do it. According to one aspect of the present disclosure, the pulse width of the energy beam 2 may range from 1 microsecond to 10 milliseconds. According to another aspect of the present disclosure, the laser pulse width may be greater than 1 microsecond up to and including continuous wave laser excitation.

The devices and methods of the present disclosure may be advantageous for applications where the environment above the absorbent membrane 3 is almost or completely enclosed. For example, Figure 4 shows a photomask assembly 102 comprising an absorbent film 3 and a pellicle 8 attached to the absorbent film 3. When the absorbing film 3 is wrapped, the method may also include directing the energy beam 2 through a material disposed close to the outer surface of the pellicle 104, which is part of the environmental enclosure of the substrate. For example, the device and method according to the present disclosure may be a method in which the pellicle 104 is an overlay of a pellicleized photomask (see FIG. 5A) comprising a pellicle film 8, a pellicle frame 9, and a pellicle frame adhesive 10. Can be used to modify .

According to aspects of the present disclosure, the method includes selecting a laser wavelength that substantially matches the strong absorption of the absorbing film 3 and setting the laser energy and pulse width to produce the desired modification of the absorbing film 3. Includes. The increased absorption in the substrate 4 allows, in some cases, lower laser energies to be used in the process, so that when the laser beam is incident or reflected from the surface of the substrate 4, the laser beam 2 This may reduce the potential for damage to adjacent materials that may interact with it.

According to another aspect of the present disclosure, a wavelength of the energy beam 2 that is highly absorbed by the substrate 4 is selected, which may be advantageous if most of the substrate has an absorbing thin film removed. Additionally, by selecting the wavelength of the energy beam 2 close to the strong absorption band of the substrate 4, the heat or temperature difference between the absorbing thin film 3 and the substrate 4 can be reduced, thereby Different thermal excitation between substrates 4 is reduced. The use of multiple laser beam wavelengths and/or laser beam energies may be utilized when multiple absorbing thin films or substrates comprised of more than one material are used. For example, multiple wavelengths can be generated by using multiple laser sources, a single tunable laser source, or both. Multiple energies can be used by controlling the output energy of each laser source using internal or external controls and/or devices.

Substrates comprised of multiple materials may require consideration of material parameters, including energy beam (2) parameters, including excitation wavelength selection. According to one aspect of the present disclosure, a laser wavelength is selected that has significant absorption in the absorbing thin film 3 material. In some embodiments, the selected wavelength is either slightly absorbed by or largely reflected by other materials on or within the substrate 4 such that the thermal energy increase occurs primarily in the absorbing thin film 3 material. This can be particularly useful in cases where the material adjacent to the absorber film is affected by the process temperature. For example, in the case of a pellicleated photomask, the pellicle film 8 and pellicle frame adhesive 10 may be in close proximity to the absorbent thin film. For example, if the pellicle frame adhesive deteriorates or outgass, it may be important to reduce the overall thermal energy or temperature rise that builds up in the system. Minimizing total thermal energy or temperature build-up is also important if significant heat is transferred to the environment (7) between the photomask (4) surface and the pellicle film (8), as this heat build-up may be transferred to the film (8). This is because it may affect the adhesive 10, the pellicle frame 9 material, or a combination thereof. In some cases, the process temperature may preferentially be maintained below the damage or modification temperature of the substrate 4 material.

In another embodiment, by basing the material modification process on the material modification process, it is particularly desirable for all regions of the substrate 4 to nearly reach the temperature typically required for modification without exceeding the thermal damage threshold of the substrate 4 or other adjacent materials. You can do it. In particular, if there is a significant difference between material absorption, it may be possible for the laser energy required to bring one of the materials to the material modification process temperature to cause thermal damage to the other material. The local fluence of the energy beam 2 can be controlled based on the material being exposed.

In another embodiment, by basing it on a material modification process, it may be particularly advantageous for different regions of the substrate 4 to reach different processing temperatures and levels. In fact, the speed and extent of material modification can vary depending on the laser energy. In this case, the local fluence of the beam can be controlled based on a desired amount of material variation in different regions of the substrate 4. Additionally, material modification may vary depending on the number of times the energy source is applied to the substrate 4. In this case, the number of applications of the energy source can be varied across the substrate 4 to produce different amounts of material modification in different areas of the substrate 4.

According to aspects of the present disclosure, longer laser pulse widths, up to and including continuous wavelength (CW) lasers, are used to improve thermal equilibrium between materials with significantly different absorption constants. However, using such long laser pulse widths produces the highest thermal energy or temperature rise in the overall system and is useful when materials adjacent to the substrate surface have thermal damage thresholds or other thermally induced effects below the process temperature. You may not.

According to aspects of the present disclosure, a laser wavelength is selected that has significant absorption in some or all of the materials on the substrate 4. For example, the same laser energy can then be used to create a desired process temperature, for example, below the damage threshold of any substrate material. It is also possible to take advantage of thermal energy or heat transfer between different materials by considering thermal properties (including diffusivity). This means that in some cases, especially if the heat energy or heat flow from the top absorber dominates the bottom absorber, the use of reduced process fluence may achieve the desired thermal modification in the substrate 4 and/or absorber membrane 3. let it be In this case, heat flow from the top absorbent to the bottom absorbent can increase the temperature of the bottom absorbent using less process energy than would be required by direct exposure of the bottom absorbent to the energy source.

Example

The following is an example of a method according to one aspect of the present disclosure applied to modifying the overlay of a photomask substrate used in a wafer manufacturing process. In this example, heat treatment according to aspects of the present disclosure may modify the thin film of the substrate and/or photomask to move the positions of features in the thin film relative to other features on the mask. This example can be used across several aspects disclosed herein.

Control of laser beam parameters may be particularly desirable in relation to overlay adjustment of the photomask. For example, wavelength selection is highly desirable due to the physical structure of a typical photomask. In some cases, the photomask assembly 102 includes a quartz substrate 4 having an absorbing thin film 3 or a partial absorbing film 3 on the critical surface of the substrate 4 (see FIGS. 1A and 1B). When the absorbing thin film 3 is a metallic film, there is generally a significant absorption coefficient for most of the producible laser wavelengths. However, in the case of partially absorbing films, unlike pure metal films, there may be a wavelength region in which these films do not absorb significantly. However, in the case of a quartz substrate 4, the substrate has significant absorption and there may be a limited wavelength range over which the laser source is generally available. Accordingly, certain embodiments may utilize wavelengths that are highly absorbed by the thin film while the substrate is weakly absorbed or transparent at the selected wavelength. This process can minimize the overall temperature rise of the system and reduce the risk of direct absorption damage to the quartz substrate.

According to aspects of the present disclosure, it may be advantageous to move features of the photomask assembly 102 to reduce errors in overlay due to mask manufacturing and utilization processes. FIG. 14 is a plan view showing a photomask assembly marked with an array of intended or designed features 110 on the surface of photomask 4. The design feature array 110 shown in FIG. 14 is schematically depicted as an array of cross (+) features. However, it will be appreciated that the cross features shown merely represent points on any photomask feature known in the art. Typically, the design feature array 110 is created by patterning a thin film 3 on a photomask substrate 4. However, patterns can be created directly on the substrate surface with or without the presence of a thin film on the surface.

In one example, the majority of the photomask is covered with an absorbing thin film 3, which may be a so-called “dark field mask”, and individual features of the design feature array 110 can be selected by moving the film only at the design feature locations. is created. In another example, the majority of the photomask has the absorbing thin film removed, which may be a so-called “clear field mask,” and the individual features of the design feature array 110 are created by leaving the thin film only at the design feature locations. . In a dark field or clear field photomask, the actual location of the features may differ from the designed pattern array, for example, as a result of variations in the manufacturing process or feature transport resulting from the use of the photomask in a semiconductor manufacturing process.

Figure 15 is a plan view showing the photomask assembly 102 according to one aspect of the present disclosure. Similar to Figure 14, Figure 15 includes a designed array of features 110, indicated by crosses, but additionally Figure 15 includes an actual array of features 112, indicated by diamonds (◇). Each actual feature in the physical array of features 112 may correspond to a design feature in the design array of features 110. Differences between the actual location of a feature from the actual feature array 112 and the designed or intended location for a corresponding design feature within the design feature array 110 may define an error in the overlay. Depending on the source(s) of error, the position of the actual pattern relative to the intended pattern may be systematic and/or random.

The overlay error may have a component in the first direction 114, a component in the second direction 116, or a combination thereof. Additionally, the total position error across all real features within the real feature array 112 may be defined according to a statistical measure across all real features within the real feature array 112, including but not limited to the sum of the errors, It may include the square root of the sum of squares, or any other statistical measure known in the art.

The dimensions of the process, the energy of the laser and the number of times each location is exposed will vary depending on the photomask's response to the process. For example, the response to applying a process initiated at a constant fluence to the entire photomask substrate 4 may be a shrinking radiation pattern as shown in FIG. 16 .

Figure 16 is a plan view showing the photomask assembly 102 according to one aspect of the present disclosure. In Figure 16, the cross (+) symbol represents the actual feature array 120 before processing the substrate 4 using an external energy source 1, and the diamond (◇) symbol represents the actual feature array 120 before processing the substrate 4 using an external energy source 1. This shows the actual feature array 122 after processing the substrate 4. The radial shrinkage of the pattern toward the center of the photomask can be seen in Figure 16. This example is only one possible result of applying the disclosed method to an entire photomask substrate 4, and is used for illustrative purposes only. Alternatively, this process may result in a radial distribution or fixed lateral movement at each position, or some other relative motion.

Figure 17 is a plan view showing the photomask assembly 102 according to one aspect of the present disclosure. In Figure 17, the cross (+) symbol represents the design feature array 110, and the diamond (◇) symbol represents the actual feature array 112. The overlay error between the designed feature array 110 and the actual feature array 112 is a pattern extending radially from the center of the photomask 4. According to aspects of the present disclosure, processing a photomask 4 with an energy beam 2 from an external energy source 1 causes the actual feature array 112 to move radially toward the center 124 of the photomask 4. You will understand that you can contract it in any direction. The results are shown in Figure 18.

Figure 18 is a plan view showing the photomask assembly 102 according to one aspect of the present disclosure. In Figure 18, the cross (+) symbol represents the design feature array 110, and the diamond (◇) symbol represents the actual feature array 112. As shown in FIG. 18 , according to aspects of the present disclosure, applying the energy beam 2 onto the photomask substrate 4 causes the actual feature array 112 to move closer to the designed feature array 110. , reducing the overlay error of the photomask assembly 102.

Continuing to apply the energy beam 2 to the substrate 4 may have a cumulative effect on the locations of the actual features in the actual feature array 112 . Figure 19 is a plan view showing the photomask assembly 102 according to one aspect of the present disclosure. In Figure 19, the cross (+) symbol represents the design feature array 110, and the diamond (◇) symbol represents further processing of the photomask assembly 102 of Figure 18 with an energy beam 2 according to aspects of the present disclosure. The actual feature array 112 is shown later. Accordingly, by applying multiple processes, the actual feature array 112 can be moved closer to the designed feature array 110, thereby further reducing the overlay error of the photomask assembly 102, as shown in FIG. 19. can be reduced.

The dimensions of the process area, the energy of the laser, and the number of times each position is exposed may vary depending on the initial overlay error of the photomask 4. For example, overlay error may occur only over a portion of the photomask 4, as shown in FIG. 20.

Figure 20 is a plan view showing the photomask assembly 102 according to one aspect of the present disclosure. In Figure 20, the cross (+) symbol represents the design feature array 110, and the diamond (◇) symbol represents the actual feature array 112. As shown in Figure 20, only the lower right portion 126 of the photomask 4 shows significant overlay error. In this case, according to an aspect of the present disclosure, processing only the lower right portion 126 or the error-affected area of the photomask 4 with the energy beam 2 means that the entire photomask 4 is treated with the energy beam 2. Without processing, it may be advantageous to reduce the overlay error in the lower right portion 126 of the photomask 4.

Figure 21 is a plan view showing the photomask assembly 102 according to one aspect of the present disclosure. 21 , the cross (+) symbol represents the design feature array 110 and the diamond (◇) symbol represents the design feature array 110 after processing the photomask 4 using the energy beam 2, according to aspects of the present disclosure. represents the actual feature array 112 from 20. As shown in Figure 21, processing of the lower right portion 126 of the photomask 4 reduced the overlay error in the lower right portion 126 of the photomask 4.

When the overlay error is more random, the localized energy and application of the energy beam 2 onto the photomask 4 according to aspects of the present disclosure, unique to discrete regions of the mask, as shown in Figure 15. It may be advantageous to vary the frequency. For this local processing of the photomask, the area of the process (size of the energy beam 2) can be advantageously adjusted to a small value compared to the distance between individual adjacent features in the actual feature array 112, The effect has a resolution that is less than the distance between individual adjacent features in the actual feature array 112. For this embodiment, the energy and number of pulses can be varied for each location on the mask such that features farther from the intended or designed location can move a greater amount than features initially closer to the intended or designed location. there is.

Additionally, when relatively fixed material changes are produced, the average material change can be controlled by treating multiple discrete areas on the substrate surface (Figure 9a). In this case, the spacing between treated areas 13 and/or the density of treated areas relative to untreated areas can be used to control the relative amount of material change processes.

A specific example of a representative method is to shift the features of the absorbing film 3 by changing one or more properties of the absorbing film 3 on the photomask substrate 4 by laser excitation. For example, in a photomask 4 _where the absorbing thin _film 3 is a _molybdenum silicon oxynitride ₍ Mo w Si It can result from change. Material changes may include, but are not limited to, oxidation, annealing, dehydration or densification of the absorbent film 3 material. Considering the level of thermal damage to the photomask, the lowest point of thermal damage is typically the melt/reflow point to the base quartz substrate, approximately 2912 degrees Fahrenheit (1600 degrees Celsius). Depending on the exact material properties of the MoSi film, material changes (e.g., annealing) may occur at temperatures much lower than the reflow point of the quartz substrate 4. Therefore, the temperature for material change can occur below the level of damage to the photomask substrate material.

As mentioned above, the relative absorption of the substrate materials is generally considered due to potential differences in material absorption properties. It may be desirable to select wavelengths that are highly absorbed by the MoSi film. Figure 2 is a schematic diagram of the absorption curve for a MoSi partially absorbing photomask film. In this example, the main absorption occurs at wavelengths below 0.3 μm or above 9 μm. Shorter wavelengths are not particularly desirable wavelength ranges because they are usually largely absorbed by air, and because they have larger photon energies, they are prone to producing multi-photon processes.

Choosing a wavelength between 1 μm and 1000 μm in the infrared region may be preferable compared to DUV because longer wavelengths reduce the potential for multi-photon processing and environmental absorption. For MoSi films, for example, it would be particularly desirable in accordance with aspects of the present disclosure to select a wavelength greater than 9 μm, around the absorption peak at 11.5 μm, which typically produces high absorption in MoSi films without high environmental absorption. According to one aspect of the present disclosure, “around the absorption peak of 11.5 μm” means a wavelength in the range of 10.5 μm to 12.5 μm, although other wavelengths in the infrared region may also be accommodated. Choosing a wavelength in this region can minimize the total thermal energy or heat input to the system while using the present invention by lowering the energy required to produce material changes.

Also, as mentioned above, consideration of absorption of the quartz substrate may also be considered. Quartz substrates used for photomasks can be specially designed to have high transmittance in the deep ultraviolet (DUV) wavelength range (see Figure 3). This is typically achieved by using synthetic fused silica substrates with very low levels of impurities. According to aspects of the present disclosure, it may be advantageous to have significant absorption in MoSi and lower absorption in a quartz substrate. As shown in Figure 3, the absorption for the example quartz substrate does not have significant absorption around the MoSi film absorption peak at 11.5 μm. Therefore, when processing at a wavelength around 11.5 μm, it is possible that thermal energy accumulation in MoSi occurs preferentially over quartz, which minimizes heat accumulation in areas of the substrate without the absorbing thin film 3, making use of the present invention While doing so, the total heat input to the system can be minimized.

Alternatively, it may be advantageous to select a wavelength that is highly absorbed by the quartz substrate of the photomask 4 such that all areas of the surface of the photomask 4 reach the desired processing temperature. Considering the thermal properties of the quartz versus absorber thin film layers, one would expect heat transfer between the materials to occur preferentially from the quartz to the absorber layer. This may occur because quartz has a relatively low thermal diffusivity, and absorbent thin films typically contain metal components and therefore have a higher thermal diffusivity. This embodiment may be advantageous when the temperature difference between the absorber film and the photomask substrate is significant. For example, differential thermal expansion between the absorber film 3 and the substrate 4 may result in damage to one or both of the materials. With different material extensions, it may weaken the bond between the absorbent thin film 3 and the substrate 4 and cause separation or peeling. If thermal equilibrium between the absorber film and the substrate is beneficial, using longer pulse widths may be advantageous to allow sufficient time for heat transfer (e.g., heat conduction) between the materials as the process temperature is achieved. .

It can be advantageous to operate at process wavelengths where quartz has significant absorption, because at the process wavelength the thermal energy flow or heat transfer takes precedence over the absorbing film (3), allowing the entire exposed area to reach the desired process temperature. . The main absorption for these substrates generally occurs at wavelengths below 0.2 μm or above 8 μm. Shorter wavelengths may be particularly undesirable because shorter wavelengths can be largely absorbed by air and have larger photon energies, making it easier to generate multi-photon processes. As mentioned above, wavelengths of about 1 μm to about 1000 μm in the infrared region may be preferred over DUV because longer wavelengths reduce the potential for multi-photon processing and environmental absorption.

For example, according to aspects of the present disclosure, it may be particularly desirable to select a wavelength of 8 μm or greater near the 9 μm quartz absorption peak, which can produce high absorption in the quartz substrate without high environmental absorption. According to one aspect of the present disclosure, “near the 9 μm absorption peak” means a wavelength in the range of 8 μm to 10 μm, although other wavelengths in the infrared region are acceptable. Additionally, this wavelength may provide advantages for photomasks with partially absorbing coatings (i.e., MoSi). As shown in Figure 2, the illustrated MoSi material has reduced absorption around 9 μm compared to the peak at 11.5 μm, and thus the decrease produced directly by the energy beam (2) from the external energy source (1). has thermal energy or temperature rise. In general, the temperature of the film material reached at the fluence of the constant energy beam 2 using a wavelength in this range should be similar to that of quartz, due to the higher absorption of quartz compared to quartz and the higher thermal diffusivity of the absorbing thin film. Additionally, this is expected to be the case even if the partially absorbing film has a relatively high absorption coefficient in this wavelength range due to the expected thermal diffusion coefficient advantage. By selecting different wavelengths in this region, it is possible to improve the overall heat uniformity by changing the relative heat accumulation of the materials produced by direct absorption of the energy beam 2 from the energy source 1.

When choosing a wavelength for overlay correction, you may also consider the type of photomask. For example, when using a dark field mask, it may be desirable to select a wavelength that is highly absorbed by the thin film. Because most of the surface is covered with a thin film, overlay modifications can best be created by modification of the thin film. When using a clear field mask, it may be desirable to select wavelengths that are highly absorbed by the substrate. Since most of the surface is not covered by a thin film, overlay modifications can best be created by modification of the substrate surface. In either case, it may be desirable to create similar thermal strain in areas of the photomask with the thin film and in areas of the photomask without the thin film so that modifications across the mask surface can be predicted.

The processes described for use in accordance with certain aspects of the present disclosure can increase the usable life of the photomask 4 by correcting overlay changes caused by use of the photomask in production and cleaning processes. If a photomask is exposed to light during use in production, the thin film of the photomask may deteriorate. This change in film composition can create a shift in the overlay of the mask. The use of the invention to correct overlay changes caused by use in production can advantageously be implemented via a pellicle (8). This allows the return of the photomask 4 to production, instead of requiring manufacturing a new photomask to replace the deteriorated photomask. Additionally, photomasks may need to be removed from production and cleaned for other reasons, which may include damage to the pellicle film and increased haze. A conventional cleaning process sequence may require removal of an attached pellicle, cleaning, and subsequent attachment of a new pellicle. The act of removing a pellicle from a mask can create changes in the overlay of the photomask. Additionally, wet cleaning processes can degrade the thin film and affect the overlay of the photomask. Using the disclosed process, it is possible to correct the position of features and effectively recover feature positions lost with pellicle removal and wet cleaning. After cleaning, when adding another pellicle to the photomask, stress is applied to the photomask, which may change the position of the features in the thin film. In this case, aspects of the disclosed process can advantageously be utilized via the pellicle 8 in the photomask assembly 102 to modify the overlay of the photomask 4.

An additional advantage of modifying the overlay of a photomask may lie in improving the transition from mask to mask. The number of wet cleanings performed on each mask can vary and depends on several production parameters. Typically, photomasks can be wet cleaned during the process necessary to create the pattern, as well as wet cleaned following a repair process to correct pattern imperfections. The final overlay will vary depending on the cumulative effect of the manufacturing process and the number of wet washes. This may result in mask-to-mask changes to the overlay before use.

According to aspects of the present disclosure, mask-to-mask variation can be improved. Different amounts of overlay correction can be applied to different photomasks to adjust each mask to the same overlay level before use. By making changes in this aspect of the photomask more stringent, the acceptable changes in other mask parameters can be increased. For example, if each photomask has a more accurate overlay, the acceptable critical dimension changes during use can be increased. This can be particularly advantageous in combination with repair treatments, as reduced dimensional control requirements can provide higher yields of photomasks.

Methods according to aspects of the present disclosure are applicable to modification of photomask absorbent films and do not require removal of pellicle 8 from photomask assembly 102. Performing modifications of the absorbent membrane after pellicleization has the advantage of ensuring that no additional wet cleaning is required prior to utilizing aspects of the disclosed process. For example, laser-based overlay modifications can be performed through the pellicle film material 8 without affecting the pellicle film properties (see Figure 4). In this case, the absorption of the pellicle film at the process wavelength and the energy density (fluence) of the energy beam 2 at the surface of the pellicle film are typically taken into account. As with substrates and substrate films, material modification processes generally do not produce a temperature increase in the pellicle film that exceeds the damage threshold. However, depending on the pellicle film, there may be significant absorption in the pellicle film around the 9㎛ absorption peak for quartz substrates. However, since the pellicle film 8 is located on top of the substrate 4 surface, it is still possible to operate in a significant pellicle film absorption region.

In addition to wavelength selection, focusing the laser beam 12, for example with a lens 11, through the pellicle film 8 and onto the surface of the substrate 4, results in a relative temperature rise of the pellicle film 8. It can be reduced (see Figure 5a). As shown in Equation 1 below, the temperature increase in the material may be proportional to the fluence of the energy beam 2 applied to the surface.

Where ΔT is the temperature change within the material and F is the absorbed laser fluence.

For constant intensity or beam pulse energy, fluence is inversely proportional to the square of the beam spot radius.

where F is the fluence, E is the energy, and r is the radius of the beam on the substrate surface.

Typically, the ratio of the beam radius 13 on the surface of the photomask 4 to the beam radius 14 at the pellicle 8 is increased by focusing the beam 2 through the pellicle 8, thus The relative fluence on the pellicle film compared to the mask substrate surface can be reduced (FIG. 5b).

In addition to considering wavelength, the use of process parameters in the system that produce large temperature rises (such as excessively long pulse lengths or high repetition rates) may be limited by the damage threshold of the pellicle membrane. Pulse width, relative fluence, process duration, and the use of external material cooling controls are examples of process parameters that can be used to minimize temperature rise in the system.

In addition to examples of MoSi-based partially absorbing photomasks, aspects of the disclosed process include photomasks, optical photomasks (with quartz only) and no absorbing thin film, and extreme ultra-violet (EUV) and nanoimprint lithography (nanoimprint lithography). It may have the advantage of sufficiently absorbing next-generation photomasks such as those used for imprint lithography (NIL). Optical photomasks without an absorbing film have features that are etched directly into the underlying quartz substrate. Additionally, nanoimprint lithography masks have features fabricated within the substrate and typically do not have a thin film. For both of these types of masks, aspects of the disclosed process can be used to create thermal strain in the substrate that leads to desirable modifications of the overlay. For thin film optical photomasks, aspects of the disclosed process can be applied to EUV photomasks by modification of the absorber or base substrate. It is also conceivable that thermal deformation of the multilayers can be used to modify the overlay. However, the level of thermal damage to the reflective multilayer must be considered, as changes in the multilayer can affect the performance of the photomask.

pulse forming

The pulse width, temporal pulse shape and spatial distribution of the laser can be used to improve material modification processes or increase the safe operating range for processing according to certain embodiments of the invention. Shorter pulse widths can be used to minimize overall heat input to the system (substrate and environment). Longer pulse widths can be used to maintain the process temperature for a long period of time, improving process uniformity and preventing temperature differences between different materials. The temporal pulse shape can be used to control the temperature rise within the absorbing film. Long temperature rises can be used to create initial effects (eg, annealing) that lead to secondary effects (eg, oxidation). Additionally, the use of multiple pulses can lower the beam energy desirable for complete processing, further reducing the risk of substrate damage similar to using longer pulse widths. The advantage of multiple pulses is that they allow the process to be run while preventing damage due to localized cooling of one material. For example, while the absorber film is not cooled and pulse-to-pulse heat build-up is used to reach the process temperature of the film, the pellicle film can be cooled to prevent multi-pulse heat build-up.

Spatial distribution of the laser beam can be used to increase process window and process uniformity. For example, Figure 6A shows a Gaussian spatial distribution 15 that can create a temperature gradient 16 within the substrate 4, while Figure 6B shows a more uniform temperature rise within the substrate 18. It has a flat top or top hat spatial distribution (17) that allows. Spatial distribution can be used to increase the process window. Having a flat top or top hat spatial distribution allows for a uniform temperature rise within the beam spot, whereas a Gaussian distribution typically creates a temperature gradient within the beam spot. To avoid the risk of substrate damage, typically the maximum energy of the beam is limited by the peak of the Gaussian distribution. If the energy change is similar to the energy difference between the process and damage energy levels, a Gaussian energy distribution is expected to have a higher risk of exceeding the material damage level compared to a flat top beam. Additionally, the Gaussian distribution can produce the effect of non-uniform material changes, whereas the top hat energy distribution is expected to produce more uniform material changes within the beam's working region.

heat management

Because aspects of the present disclosure involve heat-based processes, it is often desirable to manage the overall temperature of the system to avoid damage to heat-sensitive materials in close proximity to the processed material. This is especially true for processes that modify the material of the photomask without removing the pellicle. Pellicle membranes typically have a low thermal damage threshold. Therefore, it is often useful to avoid damage to the pellicle material and/or temperature build-up in the overall system that may transfer to the pellicle material. This includes the pellicle frame and enclosed environment between the mask surface and the pellicle membrane.

Temperature management of a system can be accomplished in several ways. The following examples represent some representative methods for sample cooling; it should be understood that other methods may exist. One way to manage system temperature is by contact cooling. For example, the photomask may be placed in contact with the plate 19, which acts as a heat sink that draws heat generated at the front of the mask toward the rear of the mask (see Figure 7). This reduces heat transfer to the environment above the mask surface, pellicle membrane, and adhesive between the pellicle frame and the mask surface. Cooling is performed by flowing another cooling fluid or gas over the mask and/or pellicle, thereby flowing a heat transfer fluid to the inlet port 21 and outlet port 20 of the heat sink, part or all of the mask and/or pellicle. It may include thermoelectric cooling or laser-induced cooling, or a combination thereof. The heat transfer fluid may be water, ethylene glycol, air, nitrogen, combinations thereof, or any other heat transfer fluid known in the art.

Another way to control temperature is by forced convection cooling. The filtered and/or cooled gas or liquid flow may be directed onto portions of the mask 24, pellicle membrane 23, pellicle frame and/or adhesive area 22 to directly reduce thermal energy or temperature build-up in these materials. (see Figure 8). This not only reduces the risk of damage to the pellicle membrane, but also reduces the risk of contaminating gas generation from the pellicle frame and pellicle membrane adhesive. In addition to hardware control of system heat build-up, heat build-up can be reduced by allowing for increased processing time. By applying slow pulses to the system or allowing a delay between the applications of a series of pulses, the injected heat can be removed without raising the overall system temperature beyond a critical level.

Thermal energy or temperature accumulation from pulse-to-pulse can also be advantageously controlled and can be varied depending on the thermal properties of the absorbing film, substrate and/or adjacent materials. In general, heat dissipation between pulses can be controlled by reducing the number of laser pulses incident on the surface per unit time. This temperature rise can also be controlled by increasing the distance between adjacent laser pulses. It may be particularly desirable for materials to have large lateral displacements between adjacent pulses, making them particularly sensitive to pulse-to-pulse thermal energy accumulation (e.g., pellicle film materials). In this case, the process typically involves positioning the laser beam 2 at approximately the same location multiple times to obtain the desired material modification of the target surface. For example, a first series of laser pulses is exposed to the surface through relatively large lateral separation (see Figure 9a). A second passage spanning the same area is arranged with an additional series of laser pulses slightly shifted relative to the first set of spots (see Figure 9b). This process continues until the entire area is exposed to the laser pulse (see Figure 9c). To fully expose the substrate 4 surface, overlap in a second direction may be used according to aspects of the present disclosure (see Figure 9D). According to aspects of the present disclosure, this entire process is repeated and/or the overlap between passages is increased, especially if the material modification process is desired to include multiple pulses to complete the process. Changing the position of the beam relative to the surface as shown can be accomplished by moving the beam and/or moving the substrate. Additionally, applying pulses in a more systematically distributed manner across the mask can further reduce the potential for thermal energy or temperature build-up on the photomask 4 (see Figure 9E).

combination of skills

The present invention can be used in combination with surface preparation or environmental control techniques to extend the life of a reticle. Some of these techniques may require processing prior to pellicle placement, while others may perform post-pellicalization. For example, surface preparation methods in conjunction with the present invention may provide increased material modification results. These process effects may result, for example, from alternating materials in the absorber film or from enhanced heat accumulation in the absorber film.

Environmental control techniques can also be used in combination with the method of the present invention. Techniques for controlling the environment both internal and external to the pellicle and pre-pellicle can be used in combination with the material modification process of the present invention. One embodiment may include replacing the environment under the pellicle with a gas that reacts with the thin film absorber and changes the material properties. This can be done without pellicle removal by gas exchange through filtered vents on the pellicle frame. Additionally, in conjunction with the present invention, it may be advantageous to maintain an inert environment inside or outside the pellicle to improve bulk absorbent properties compared to surface material modification processes. These combined processes can, for example, increase the direction of relative overlay changes or feature shifts.

metrology

Methods according to aspects of the present disclosure can be used in combination with metrology to monitor critical process parameters and/or evaluate the progress or completion of a material modification process. Measurement of the temperature generated locally in the substrate material can be used, for example, in combination with material changes. To determine the risk of temperature-related measurement damage, temperature measurements can be evaluated prior to process application. These temperatures can also be monitored during the material modification process to ensure process control and/or reduce the risk of material damage. For example, according to certain embodiments of the invention, the temperature of the substrate and/or absorber film may be monitored during the process and the applied energy may be controlled to maintain the desired process or to turn the process off if too large a temperature buildup is detected. You can give feedback. A number of devices and methods exist for monitoring temperature, including contact (30) (e.g., thermocouples) and non-contact (29) (e.g., infrared cameras) devices and methods (see FIG. 10).

Additionally, in accordance with aspects of the present disclosure, the metrology apparatus 31 and method may be used to treat a material or a substrate and/or a material adjacent the substrate before, during and/or after the energy beam 2 is applied to the substrate 4. It can be used to analyze or monitor the performance characteristics of (Figure 11). For example, measuring the positions of features on a photomask can be used to calculate overlay error before processing. This can be used to determine the level of material correction needed to correct local or global overlay errors. Additionally, it can be used to determine the exact energy or number of pulses to be applied to discrete areas of the photomask to induce the desired change. Additionally, this metrology can be used to monitor overlays during processing and feed information back to the process or stop it if adjustments are within predefined process limits. Additionally, by monitoring the material properties of the pellicle membrane, it is possible to determine whether any adverse effects occur on the pellicle material. This information can be used before processing to limit process temperature, or during processing to stop the process if damage is observed. For example, one or more polarization analyzers can be used to measure the material response of the pellicle film, absorber film, and substrate surface. Next, this data can be used to calculate desired material properties including film thickness, transmittance, and topology. It is possible for the measurement device to share a common optical path with the process energy source (Figure 12). For example, the energy source 1 may be coupled to the path of the measuring device 31 using a beam splitting device 33 . Additionally, additional optical elements 2 may be beneficial to properly collect metrology data, as shown in FIG. 12 .

For example, in the case of photomasks, multiple metrology may be incorporated into the material modification process according to certain embodiments of the present invention. For example, by identifying the overlay error of the entire photomask reticle, processing temperature requirements can be specified. Identifying local or global overlay changes on a photomask can be used to determine the lateral dimensions for process applications and the multiple energy levels needed to process different locations/sections across the photomask. Additionally, it may be beneficial to initially apply a low energy process to measure the response of the photomask features to the process. Once the magnitude of the response to a particular mask has been measured, further processing can then be applied using this information. This allows the per-mask response to be considered when determining the best process for modifying the overlay of the photomask.

Metrology according to certain aspects of the present disclosure may also be used to monitor properties of materials adjacent to the surface being cleaned. For example, the temperature of the pellicle film on top of the photomask can be monitored to reduce the risk of damage to the pellicle film. Additionally, the permeability properties of the pellicle membrane can be used to achieve treatment effects during or after treatment.

As those skilled in the art will recognize when practicing one or more aspects of the present disclosure, the foregoing metrology examples are not intended to be exhaustive. Rather, these examples merely represent the use of metrology within some methods according to the present disclosure.

The metrology device 31, the external energy source 1 or a combination thereof may be operatively coupled to a controller 40 for their control. Controller 40 may be any processor specifically designed to perform operation or control of metrology device 31, an external energy source, or both. It will be appreciated that the controller 40 may be housed in a single housing, or multiple housings distributed throughout the excitation and metrology apparatus. Additionally, module controller 310 may include power electronics, preprogrammed logic circuitry, data processing circuitry, volatile memory, non-volatile memory, software, firmware, input/output processing circuitry, combinations thereof, or any known in the art. It may include the structure of other controllers.

It will be appreciated that controller 40 may be configured to perform or control any method or function described herein. Additionally, an article of manufacture comprising non-transient machine readable instructions that, when executed by controller 40, cause controller 40 to perform or control any of the methods or functions described herein. You will understand that you can configure .

Device

Certain methods for modifying materials according to aspects of the present disclosure may be practiced using various aspects of the devices described herein. One example of such a substrate manipulation device 130 uses a conveyor 34 to position a substrate 4 sample relative to an external energy source 1 along one or more axes of movement, as shown in FIG. 13 . It additionally includes robotic handling 35 of the substrate 4 material and/or movement of the substrate 4 . Robotic handling may include a substrate-grip end effector 36 for transferring the substrate 4 between locations. The device 130 may include, for example, one or more of the metrology described above and/or may include a way to control the temperature of the substrate and/or adjacent material during the material modification process. Additionally, the device may comprise a metrology used to present the substrate to the staging system and thus to the laser beam (2). Additionally, the metrology may include a computer-controlled visual recognition system. Additionally, the device may utilize computer control of lasers, motion and/or metrology, and may provide software-based recipe control of the material modification process. Controlling the laser energy source may include, for example, controlling the amount of energy applied during the process, as well as when the laser pulse is applied.

Reticle manufacturing process

Methods and/or devices according to aspects of the present disclosure may be used as part of a new reticle manufacturing process that includes modification of an overlay on a photomask surface. According to aspects of the present disclosure, a material modification process may be used to adjust the overlay during or after a photomask manufacturing process, including photomask repair processing. The photomask may or may not be pellicleated prior to processing. Certain embodiments may also be applied to photomasks after a cleaning process. According to aspects of the present disclosure, material modifications may be used to correct overlay changes resulting from wet cleaning processes. As a result, this process can be used to modify the overlay to bring the photomask to the desired specifications for use in production. Other aspects of the present disclosure can be used after a reticle has been used in production to correct overlay changes caused by use in production. This process is applied through the pellicle to correct the overlay, thus avoiding the pellicle cleaning process. In this embodiment, aspects of the disclosed process can extend the life of the photomask beyond what is currently achievable, by avoiding additional wet cleaning processes and/or re-pellicling(s). Since photomasks that are out of specification must be discarded, a set of duplicate photomasks is typically required. Accordingly, the disclosed method may also provide cost savings by extending the useful life of the photomask and reducing the requirement for replica masks to complete a manufacturing run.

A new photomask reticle manufacturing method according to certain aspects of the present disclosure includes an apparatus that utilizes one or more of the methods discussed above to modify the properties of the absorbent thin film 3 of the photomask 4. A typical reticle manufacturing process according to aspects of the present disclosure includes multiple wet cleaning processes applied to the photomask during manufacturing. Because the number of wet cleaning processes varies from mask to mask, there is final overlay variation between masks. One aspect of the present disclosure utilizes one or more of the material modification methods described above to globally vary the overlay of each photomask by a different amount such that the final overlay variation between masks is reduced. According to another aspect of the present disclosure, a reticle manufacturing process comprising one or more of the disclosed methods can be used to extend the useful life of the photomask 4 by reducing overlay errors (globally or locally).

In addition to the variation in optical performance from mask to mask, each wet cleaning process can add variability to material properties across a single photomask surface. It is possible that the variability of the overlay on a single photomask after manufacturing and/or wet cleaning processing is outside acceptable limits. This is especially true as the number of wet cleaning processes increases. According to one aspect of the present disclosure, a new photomask reticle manufacturing process is provided that includes an apparatus that utilizes one or more of the material modification methods described above to improve the uniformity of the overlay of the photomask. This may include creating non-uniform changes across the entire photomask or one or more localized changes within the overlay. According to certain embodiments of the present invention, non-uniform material changes are used to extend the useful life of a photomask by correcting non-uniformities within the overlay of the photomask.

According to certain embodiments of the present invention, a new reticle wafer manufacturing process extends the life of photomasks, thereby reducing the use of additional masks or sets of masks for product manufacturing.

Many features and advantages of the invention are apparent from the detailed description, and it is therefore intended that the appended claims cover all such features and advantages of the invention as fall within its true spirit and scope. Additionally, since many modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and thus all suitable modifications and equivalents are to be considered within the scope of the invention. there is.

Recitation of ranges of values herein are intended to serve only as a shorthand method of referring individually to each individual value within the range, unless otherwise indicated herein, and each individual value is listed in the specification as if it were individually recited herein. It is integrated. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.

Unless otherwise specified, the word "substantially" as used herein means "to a significant extent" or "to the extent necessary but not as much as specified."

It will be understood that the foregoing description provides examples of the disclosed systems and techniques. However, it is contemplated that other implementations of the present disclosure may differ in detail from the examples described above. Any reference to the disclosure or examples thereof is intended to refer to the specific example being discussed at the time and is not intended to imply any limitation on the scope of the disclosure more generally. Any language of distinction or disparagement regarding a particular feature is intended to indicate a lack of preference for such feature, but is not intended to exclude it entirely from the scope of the present disclosure, unless otherwise specified.

Claims (20)

As a method of improving the performance characteristics of a photomask,
The photomask has one or more features disposed thereon,
The one or more features have an associated design location,
The distance between the location of the one or more features and the associated design location defines a location error of the one or more features, the method comprising:
directing electromagnetic radiation having a wavelength substantially matching the highest absorption coefficient of the photomask toward the photomask;
generating an increase in thermal energy in the photomask through incidence of the electromagnetic radiation;
Reducing the position error as a result of increased thermal energy in the photomask,
A partially absorbing thin film is disposed on the photomask, and the one or more features are included in the partially absorbing thin film,
The one or more features include a first feature disposed at a first location and a second feature disposed at a second location different from the first location, the method comprising:
reducing a position error of the first feature by a first amount;
Further comprising reducing the position error of the second feature by a second amount,
wherein the first amount is different from the second amount. According to clause 1,
The method further comprising directing the electromagnetic radiation through a material located on top of the photomask. According to clause 2,
The method of claim 1, wherein the photomask is at least partially enclosed within a pellicle, and the material is a pellicle film. According to clause 1,
The method of claim 1, wherein the electromagnetic radiation is a laser wavelength exceeding 8 micrometers. According to clause 1,
The method of claim 1, wherein the photomask is a quartz photomask, and the electromagnetic radiation wavelength is about 9 micrometers. delete According to claim 1,
The thin film partially absorbs light. According to clause 1,
The method of claim 1 , wherein the reduction in position error is a result of one or more of dehydration, oxidation, annealing, and densification. delete According to clause 1,
The method of claim 1, wherein the photomask includes a plurality of materials, the electromagnetic radiation is a laser beam, and the laser beam has a wavelength that substantially matches the highest absorption coefficient of two or more of the plurality of materials. As a method of improving the optical properties of a photomask,
directing electromagnetic radiation having a wavelength substantially matching the highest absorption coefficient of the photomask toward the photomask;
generating an increase in thermal energy in the photomask in response to incidence of the electromagnetic radiation;
A method comprising modifying the position of a first feature on the photomask relative to a second feature on the photomask,
Here, the photo mask has a partially absorbing thin film disposed thereon,
The one or more features include a first feature disposed at a first location and a second feature disposed at a second location different from the first location, and the method of modifying the location includes
reducing a position error of the first feature by a first amount;
Further comprising reducing the position error of the second feature by a second amount,
wherein the first amount is different from the second amount. According to claim 11,
The method of claim 1, wherein the modifying step includes increasing the distance between the first feature and the second feature. According to claim 11,
The method of claim 1, wherein the modifying step includes reducing the distance between the first feature and the second feature. According to claim 11,
wherein the photomask is at least partially enclosed within a pellicle, the method further comprising directing the electromagnetic radiation through a pellicle film positioned on top of the photomask. According to claim 14,
The method of claim 1 , wherein electromagnetic radiation is further directed toward the thin film, wherein the electromagnetic radiation has a wavelength that substantially matches the highest absorption coefficient of the thin film. delete delete delete delete delete